Watermarks and Copyright

What is Watermarking?

Watermarking is defined as placing information or data within a media file of any kind, Picture, Audio or Video. The watermarks are placed within the file in such a manner as to not affect the files function. Thus the Watermarked MP3, Picture or Video still function as Audio, Pictures or Video Files with the watermark in place. [VS]ⁱ

How does watermarking Work?

Steganography

Petitcolas states that modern steganography originates in 1665[PF]ⁱⁱ; the notion of hiding information in plain sight dates back to antiquity as militaries of all empires had to communicate across potentially “insecure” messengers; the term “Marathon” is actually from Greece where a solder named Pheidippides ran form Marathon to Athens a distance of 40 km and is said to have died after the run from marathon to Athens to give word that they had beaten the Persians. The Spartans used a “Cipher” stick as a means to encode and decode messages in either cloth or paper wrapped around it, if the paper or cloth had a pattern on it other than the message than we may assume that the message may have been steganographic in nature. Steganography is essentially the art of hiding information that is significant in the areas of data files usually in pictures, but they can also be audio or video files.

Least Significant Bit Manipulation

In binary, the lest significant bit is the on the right hand side, as it is either only a 1 or a 0 regardless of how large the number is. Changing the LSB has negligible impact on a JPG or BMP or GIF file if it’s done across multiple bytes of the image equally spaced throughout the image.[SB] ⁱⁱⁱ

Algorithms and Transformations

Most steganographic techniques involve the use of complex algorithims or transformations where the desired data to be hidden is planted in the file by either a propritary algorithm or a transform to the data that affects an insignificant portion of the file.

Masking and Filtering

Masking and filtering are alternate methods used to also hide information in images or data in transit where statistical analysis may be used. [DB]^iv [TZ] ^v

CDMA Blind Wavelet

There are many methods that one may use to watermark a file; recently, Maity et al. proposed the use of CDMA based blind wavelet transforms to the LL and HL bands of a media file; ie; a movie with CDMA encoded Text is a reliable method to hide information as well. The encoder and decoder would have to work on the same media files. [MS]^vi

If i wished to hide information in an image or mp3 or Video file, i would first encrypt the message using AES via PGP, if it intended audience is a known associate of mine I'd grab their public key. Then using an application and codebook based transfer i would send a first message to the intended audience with a an encytped hint along the lines of the software needed to unencrypt the next message or I'd encrypt the photo and send it for analysis.

Stego Magic is free, I came across in this archive:

http://members.cox.net/ebmmd/stego/stego/softwarewindows.html

I would use it as it's the easiest client to use, however I'd add the ascii armoured text to the file as the steganographic message. The password would either be encrypted and sent; or would be transferred in an out of band channel.

My messages would be limited in size however Twitter get's the news out with only 140 characters, I'm sure I could manage to communicate with the same amount. 

By encrypting the message I would be creating a 2^nd layer of anti-forensics; the first layer would be fact that it's hidden in plain sight in a picture; the second aspect would be that it uses AES on top of being hidden. An interesting side note is that XINE, an open-source media player has a plug-in to render HD content in ASCII; it make's for excellent key's for symmetric one way encryption; so you can use a movie reference as a secret message containing an out of band key that uses a reproduce-able 1080P based signal rendered in Ascii as it's decryption key. The difficult part is getting the reference in SMPTE timing but that's what codebooks are for.

Refrences

i [VS] Van Schyndel, R.G.; Tirkel, A.Z.; Osborne, C.F.; (Department of Physics, Monash University, Clayton, Vic, IEEE international Confrence on Image Processing Proceedings ICIP-94, November 1994) A digital Watermark [Online] World Wide Web, Available from: http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=413536 (Accessed on July 16^th 2011)

ii [PF] Petitcolas, Fabien (Peticolas.net, January 2011) Hisotry of Steganography and Cryptography [Online] World Wide Web, Available from: http://www.petitcolas.net/fabien/steganography/history.html (Accessed on June 16th 2011)

iii [SB] Si, Brigitte (Athabasca University, 2004) Introduction to Steganography [Online] World Wide Web, Available from: http://www.infosyssec.com/infosyssec/Steganography/basics.htm (Accessed on June 16th 2011)

iv[DB] Dunbar, Brett (SANS, January 18^th 2002) A detailed look at Steganographic techniques and their use in an Open-Systems Environment http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.157.3117&rep=rep1&type=pdf [Onlline] PDF Document, Available from: (Accessed on June 16^th 2011)

v [TZ] Radhakrishnan, Regunathan; Kharrazi, Mehdi; Memon, Nasir; ( SpringerLink, The journal of VLSI Signal Processing, Volume 41, Number 3, P 293-303 ) Data Masking: A New Approach for Steganography? [Online] PDF Document, Available from: http://www.springerlink.com/content/p7r415u7876037jx/ (Accessed on June 16^th 2011) DOI: 10.1007/s11265-005-4153-1

vi [MS] Maity, S.P; Kundu, M.K; Maity Seba (ACM, 2009) Dual purpose FWT domain spread spectrum image watermarking in real time [Onine] PDF Document, Available from : http://portal.acm.org/citation.cfm?id=1507867 (Accessed on June 16^th 2011)